This invention relates to copper electrochemical plating in general and more particularly to maintaining the stability of the plating electrolyte.
In electrochemical copper plating in an IC process, the stability of electrolyte plays an important role on the film property. Some commercial copper plating machines have no working method to solve the maintenance of the electrolyte; they just drain and replace the electrolyte at great cost. Others maintain the purity of the electrolyte by a method that leaks a percentage of the old electrolyte and refreshes the leaked percentage with new electrolyte during the plating process. This method is asserted will maintain a more stable electrolyte property.
U.S. Pat. No. 6,099,702 issued to Reid et al on Aug. 8, 2000 is entitled xe2x80x9cElectroplating Chamber with Rotatable Wafer Holder and Pre-wetting and Rinsing Capabilityxe2x80x9d teaches a plating cell with an inner plating bath container. A wafer on a wafer holder is lowered into a position in the inner plating bath to a position below a plating solution level. After electroplating, the wafer is raised and spun so that the spun-off water and plating solution enters either a reclaim or a waste inlet in the plating machine. In this patent the pre-rinse stage returns substantially all of the rinse solution back into the plating solution.
U.S. Pat. No. 5,660,699 issued to Saito et al on Aug. 26, 1997 is entitled xe2x80x9cElectroplating Apparatusxe2x80x9d teaches a cathode base for supporting a substrate, and a damper for clamping a peripheral edge portion of the substrate together with the cathode base. The plating solution is supplied onto the substrate so that the surface of the substrate is plated. A negative pressure source clamps the substrate by drawing the damper under a negative pressure through a suction conduit.
U.S. Pat. No. 6,077,404 issued to Wang et al. on Jun. 20, 2000 is entitled xe2x80x9cReflow Chamber and Processxe2x80x9d teaches the introduction into a re-flow chamber a material that is at least as reactive or more reactive than a material to be re-flowed (i.e. a gettering material). The gettering material is sputter deposited within the re-flow chamber while a shield prevents the gettering material from reaching the material layer to be re-flowed.
U.S. Pat. No. 6,027,631 issued to Broadbent on Feb. 22, 2000 is entitled xe2x80x9cElectroplating System with Shields for Varying thickness Profile of Deposited Layerxe2x80x9d teaches an electroplating system including shields for controlling the thickness profile of a metal electrodeposited onto a substrate. The shields are position between the anode and the cathode in a standard electroplating apparatus with a device for rotating the plating surface.
U.S. Pat. No. 6,156,167 issued on Dec. 5, 2000 to Patton et al. is entitled xe2x80x9cClamshell Apparatus for Electrochemically Treating Semiconductor Wafersxe2x80x9d teaches an apparatus having a cup with a central aperture defined by an inner perimeter. A compliant seal member is adjacent the inner perimeter for pressing against the substrate. A plurality of electrical contacts adjacent the compliant seal member makes electrical contact with the substrate. A cone member is attached to a rotatable spindle so that the cup and the cone define a cavity with the plurality of electrical contacts located therein. In addition a pressurized gas is contained in the cavity. The seal member forms a seal with the perimeter region of the wafer surface preventing plating solution from contaminating the wafer edge, wafer backside and the contacts.
U.S. Pat. No. 6,284,121 issued to Reid on Sep. 4, 2001, is entitled xe2x80x9cElectroplating System Including Additive for Filling Sub-Micron Featuresxe2x80x9d teaches a standard electroplating apparatus using an acid copper bath with an additive for leveling. The additive is chosen to have molecules of a size that is about the size of the features to be filled by the electroplating process. The relatively large size of these additive molecules tends to hinder the mass transfer of the additive molecules into the features. Consequently, the additive molecules are preferentially absorbed by the surface of the plating surface relative to the inner surfaces of the features. The electroplating process tends to fill the features relatively quickly compared to the other parts of the target surface so that all of the surface area of the target is equivalent in height. With little or no additive molecules within the features, the features tend to be filled without voids.
U.S. Pat. No. 4,435,266 Issued to Johnston on Mar. 6, 1984 entitled xe2x80x9cElectroplating Arrangementsxe2x80x9d teaches a particular electroplating arrangement having use in the manufacture of stamper plates for disc record production. This apparatus teaches the flow path from the reservoir through the anode area for cleaning the anode bag and removing suspended impurities. The impure electrolyte subsequently passes out of the cell through a valve where it is filtered before returning to the reservoir. This is similar to FIG. 1 herein below.
It is submitted that none of the above patents discuss maintaining the purity of the electrolyte. In those systems that attempt to maintain the purity of the electrolyte, there is a process for maintaining the purity of the electrolyte that have as one disadvantage a higher electrolyte cost by requiring more electrolyte and another disadvantage of having to disposed of the removed electrolyte or waste electrolyte.
It is therefore an advantage of the preferred embodiment to control the electrolyte stability in a copper electroplating process with a very economical procedure.
It is yet another advantage of the preferred embodiment to provide an in-line and real-time control of the organic compounds and impurities in the electrolyte during the plating process.
These advantages are solved by a system for maintaining stable plating performance in copper electrochemical plating comprising an electrolyte tank containing the copper-plating electrolyte. An electroplating cell adapted to receive IC devices to be plated, receives the copper-plating electrolyte from the electrolyte tank.
A first valve is interposed the cell and a micro-filter and is operable to control the flow of the copper plating electrolyte from the cell to the micro-filter.
A second valve is interposed the cell and a carbon-filter and is operable to control the flow of the copper plating electrolyte from the cell to the carbon-filter for removing additives from the electrolyte.
A programmable controller has a memory, several input circuits, valve control circuits, output circuits, and analysis control circuits and is operable to control the first and second valves in such a mutually exclusive manner that the copper plating electrolyte flows from the cell to only one of the filters.
An algorithm is stored in the memory of the programmable controller and is responsive to the several inputs measuring the plating process for opening one of the valves and closing the other of the valves for controlling the flow of the copper-plating electrolyte.